Design And Implementation Of Wideband Spectrum Monitoring System For Sub-Nyquist Sampling

Wide band spectrum monitoring detects various spectrum resources in complex electromagnetic environment by the receiver.It has great significance to study the design of wide band spectrum monitoring system whether it is in the civilian and military field.However,with the rapid development of electronic communication technology,the frequency and bandwith of the signal is more and more high.According to the traditional Nyquist sampling method,the existing ADC sampling rate,digital processor and memory are difficult to meet the demand of ultra-wideband spectrum monitoring.Modulated Wideband Converter(MWC)based on the theory of compressed sensing can use much lower than the Nyquist rate sampling rate for blind sampling of the wideband sparse signal,and to reconstruct the original signal by the reconstruction algorithm.It is widely used in the design of wideband spectrum monitoring system.The research content of this paper is to design MWC-based wideband spectrum monitoring system for Sub-Nyquist sampling,which mainly includes the following aspects:Firstly,for the non-ideal factor of MWC hardware circuit,the simulation model of non-ideal factor is established for mixer,low-pass filter and ADC.The cause of non-ideal factors is analyzed.Through simulation experiments,the relationship between reconstruction probability and non-ideal factors is studied.The simulation results show that if the number of channels is enough,the adverse effects of non-ideal factors on the system will be exploited and the system will be optimized.The influence of non-ideal factors on the system is studied,which has a certain significance for the hardware system of MWC.Secondly,according to MWC hardware prototypes,the overall designed architecture of the system is proposed,then the framework of the hardware implementation and the specific parameters of the system are given.And the four channel MWC hardware board design was completed.The circuit module design in analog front end of MWC and the power module design of the system were introduced.The high-speed pseudo-random sequence is generated by Gigabit Transceiver X(GTX)of FPGA.It can be seen from the time-domain waveform and spectrum that the high-speed pseudo-random sequence produced by this method can meet the requirements of MWC system for processing wideband sparse signals.Thirdly,for 50MHz-500 MHz wideband sparse signal,using oscilloscope and PC software to test the four channel MWC hardware system with the low sampling rate of 83.3MHz.The test results show that the system can effectively recover the single carrier signal,QPSK signal and mixed signal of single carrier signal and QPSK signal spectrum,and it has good performance on reconstruction of wideband sparse signals.